Fan



y 1932- F. LJUNGSTROM 1,863,113

FAN

Filed May 29, 1931 2 Sheets-Sheet l INVENT R y 1932- I F. LJUNGSTROM FAN Filed May 29, 1931 2 Sheets-Sheet 2 Patented 19,

UNITED STATES.-

PATENT. OFFICE or srocxnom, SWEDEN, A

CORPORATION OF SWEDEN FAN Application filed Kay 29, 1931, Serial K0. 540,931, and in Sweden September 22, 1980.

My invention relates to fans and more particularly to the type of fan or difl'usor .Which is used in a room, such as a room of a home-or an 'ofiice, for producing a movement of air for cooling purposes, which type of fan may be referred to as domestic. However, my improved fan is not limited todomestic use, but is also applicable to commercial uses. f

The average electric fan of the domestic type comprises stifi metal blades. Invariably these fans are surrounded by a guard for the reason that an unprotected fan is a source of danger. It is.one object of my invention to do away with a guard for a fan.

To accomplish this I have devised a fan including blades or vanes or wings of nonelastic flexible material. At the same time the aim of the invention isto provide a fan which is stable and steady in operation. To this 'end, I combine with the soft flexible vanes a form of construction which gives stability to the fan structure.

Not alone in domesticfans, but in commercial fans of larger size, there is a danger of accident from the use of rigid fan blades. This is true, for example, of automobiles and air planes. My improved fan is applicable to various uses where it is desirable to eliminaterisk of accident due to a fan and at the same time to have a fan which is stable in operation.

A further'object of my invention is to provide a portable fan. which requires the minimum of space and which can be folded up for carrying purposes to small size.

In the preferred form of my invention-I provide vanes made of ribbons or strips of cloth. chamois skin, canvas, duck or other fiexiblc and limp or non-elastic material. These ribbons are attached to a hub ataxially disposed points and are loose or slack between their places of attachment to pro-. vide loop'blades adapted to be thrown out by centrifugal force in a manner analogous to that of a jump rope as used by children. In general, it may be said that this causes the ribbons or vanes or blades to take on a 56 shape which maybe appropriately called a similar length held by a child at play, it will centrifugal catenary. Assume a chain or rope secured at its ends at spaced points on a rotating shaft. The curve of the rope or chain is determined essentially by the resultant of the centrifugal force and the ten- 55 sile forces within the rope or chain. If a number of chains or ropes are so arranged and side by side with respect to each other so as to simulate a number of jump ropes of 'propriate to say that such a strip takes on a shape defined by the term centrifugal catenarv.

If this rotating wing or blade is subjected to lateral pressure, for example, air pressure. the catenary curve is displaced somewhat fromits symmetrical balanced position with respect to the two points ofsupport at the end of the curve. but if the rope, or chain. or strip. is of suflicientlv heavy material. this displacement of the catenary' curve becomes small because the centrifugal force, when the catenary curve assumes an oblique position. counteracts the displacing force in such manner that the internal tensile stresses oppose the external displacement forcesi If a fan bladeconstructed according to this'principle, be studied, it will be found that when the speed is changed, the fan is always able to permit an increased lateral pressure on the blade, inasmuch as the centrifugal force, as well as the air pres-' sure produced on the blade, increases in accordance with the square of the velocity. My invention will be made clear by reference to the accompanying drawings, forming partof this specification and in which are illustrated preferred forms and adaptations of the invention. I

Referring to the drawings:

Fig. 1 is a front view of. arm in accordance with the invention;

Fig 2 is a side view-taken on the line 22 Fig. 3 shows one manner offastening together the ends of the ribbon forming the blade,

ing the invention; and

Fig. 9 shows a fan embodying the invention applied to the cooling of the radiator of an automobile.

Referring m P y' to. -F .g and 3, reference character 10 d i cylindrical hub having an apprecia 1e axial extent. Hub 10 is mounted on a shaft 11, which ma be rotated by any suitable-prime mover.i ecured to the hub 10 are a plu'-. rality of vanes or blades 12. These .blades are made of strips or ribbons of limp or non-elastic flexible material, the weight and strength of which may vary with diflerent sizes of fans. Preferably the material. is relatively stron and sturdy such as heavy cloth or it may he made of what'is known as canvas or duck.' As shown, the strips used are parallel edged, but this'not' a. prime requisite.

points or plates (-13 and 14). In the form 0 ,shown, these-points are spaced both axially and circumferentially. The average. axial displacementisjindicated by a. The average peripheral or "circumferential displacementis indicated by b. Theplaces of at-', tachment 13 and 14 are determined by slots in the hub. .The strips pass through these slots and are riveted or sewed together at I 15. -The slots, as shown in Fig. 2, are obliquetothe axis of rotation 0-0. It follows, from whathas been-said above, that the slots are axially and 'cirbumferentially disposed. by the distances a and b, respectively. -Asshown in Fig. 2, the slotsare somewhat curved.

This, it will be understood,.is in accordance with recognized fan blade or propeller design since the ribbons are to act like rigid blades to cause a current of air in the general direction of the arrow 7. The slots at 13 and- 14 need not be exactly parallel. but the slot at 13 may be slightly -more inclined to the. axis q than the slot at 14, to take care of the in crease invelocity .of the air stream after leaving what may be terrhed the forward blade section at-14 and approaching the after bladesection at 13.

slightl ates a Strips 12 are secured to the hub 10 at spaced u When the fan is at rest the blades are limp, being made of soft material, such, for exam le, as herringbone-woven coarse, cloth,

an may assume position such as indicated at. 12a. When the hub is rotated, theblades are thrown out, due'to centrifugal force, andassume a form substantially as shown in full lines in the drawing. It will be seen that the curve is substantially acentrifugal catenary,

as above defined, being slightly displaced'oppositely with respect to the direction of an flow on account of the lateral air pressure.

The symmetrical position is shown in a dotted l ne 9 The actual position deviates tent o displacement is not great and may vary somewhat in accordance with the kind of material used for the ribbon blades. The axial displacement of the points of attach-- -ment causes. the blade structure to become relatively ri 'd. It will be seen that if a were used, as in an ordinary fan blade made ofsoft material, it would be bent backwards. '.by' the reactionary force of the and would not have stability. The arched" construction obtained by the axial'displace-. ment of the points of attachment of the ribair pressure bon provides-a support for the fan blade.

In the arrangement shown in Figs. 1 and 2,, the effective lengths of the blade, that is, the

arched portions, are at least three times as long as the distance between the slots. This proportion may be varied and difierent characteristics may be obtained by varying the 'free length of ribbon with respect to the distance between slots. If desired, the cloth ribbon may be suitably edged.

It will be seen that no guard is provided for the reason that no guard is necessary. Even though the fan is rotated at high speed by an electric motor, a finger may be inserted or caught in the ribbon vane and 'no injury will be done. Even if there is a direct mechanical connection to a. powerful prime mover, the

fan blade may strike an object and'yet there is no danger of injuryto materials since the fan blade, being made of soft material, can be deflected. A fan of this type can be made with muchgreater diameter'than an ordinary from this dotted line 9. The exsingle straig t piece made of soft material rigid fan. Consequently it. can circulate larger quantities -ofi air than a smaller fan with speedier and more intensive air circulation, and it is better suited to spread a 'pleasant breeze in a room of a dwelling.

In Figs. 4 to 7 inclusive, is shown a complete portable or domestic electric fan em-.

bodying' the invention. This .fan comprises a base 20. Pivotally secured to the base 20 is v an upwardly extending arm 22, to the upper end of which is secured on electric motor 23. Moto 23- is provided with'an armature shaft 24 towhich is secureda hollow hub 25. Hub 25 is of such dimensions and so formed as to substantially enclose motor 23.. Hub'2'5 is lac provided witha bushing 26 secured thereto by means of screws 27, .which bushing is in turn secured to shaft 24 by'means of a set screw 28, which may be made accessible from outside the hub through a hole 29. Hub 25 is preferably'ma'de of a phenol condensationcase, the vanes are secured to the hub by being folded over and sewed at the ends 50. It will be obvious that various ways may be used to secure the vanes in the hub. The slots 30 are shown as arcuate, but it will be understood that they may be straight. The slots are axially and circumferentially spaced and extend obliquely with respect to the aix's of the hub. It will be understood that-axial displacement is more important than peripheral displacement. and though peripheral displacement is preferable, it is not necessary;- ach slot terminates in a circular hole 31, which makes it possible to insert or remove a vane without removing the hub from the motor and for the purposepf facilitating replacement. It may be advisable in certain cases to use glue or other material for more firmly holding the vanes in the slots. Instead of sewing over the ends, it is also possible to provide other securing means as by bending over the ends of the ribbons and fastening them to the hub or using metal fasteners having teeth.

The base 20 is provided with an opening 5 37 through which passes an electric cord 38 comprising two conductors. One of the conductors passes directly to a passageway 39 "within arm 22 to one terminal of motor 23.- The other conductor is led to a terminal of a.

rheostat 21 within base 22. The other terminal of the rheostat 21 is connected to the mo-' tor 23 by a second conductor passing through arm 22. Rheostat 21 may be of any desired type and ishere shown as being provided' with three contact points 44. Journalled in base 20 is avertical pin 40 to the upper end of which is secured a handle 41 and to the lower end of which is a spring contact member 42. Handle 41 is ada ted to be rotated.

or turned between points limited by stops 43. Upon rotation of handle 41, member 42is caused to successively contact the points 44 on the rheostat; When member 42 is in the position shown in dot and dash lines 'in Fig. 7 the circuit is open and the fan is not operating. Upon movement of member'42into 'contact with the first point 44, as shown in full in Fig. 7, the circuit is closed through the rheostat, all the resistance ,of the rheostat being in the circuit, and the motor. operates at low speed. Upon movement of the member 42 into contact with the next point, a portion .of the resistance is shunted and the speed of the motor increased. Upon contact with the next point, further resistance is shunted, while contact with the last point shunts'the entire rheostat and the motor operates at full speed. Obviously, the invention may be embodied in a fan which does not use a rheostat.

The bottom of base 20 is closed by means of a plate.45 which-may be secured to the base by screws 46. Around the lower edge of the base is placed a ring 47 of rubber or the like which rests upon the surface, such as-a table, whichsupport the fan.

When the fan is not operating, the blades are limp, as described in connection with the embodiment of Figs. 1 and 2. .Upon rotatlon of the fan, the blades assume a position substantially as shown. The operation of'the I fan is the same as described in connection with Figs. ;1 and 2 and it is not necessary to here repeat it:

If necessary, in order to cool the electric motor, the windings may be designed to give -a fan action and holes as at 65 and 66 may be provided for allowing passage of air. If desired, a separate fan element may be used for cooling the motor or the hub 25 may be so made as to produce 'air circulation, as with integral oblique vanes inside the openings in the cone-shaped head.

The arm 22 is formed with a rounded bottom portion 67 which seats in a, correspondingly curved recess 68 in an upper extenslon of the base member 20. A spring 69 pivoted to the base member and to a pin 70 in the arm 22 serves to pull arm 22 downwardly into the opening 68. Friction of the parts holds arm 22 in any position in which it is placed by hand. The joint formed by the part 67 and the journalled surface68 is preferably such that themotor may be folded downwardly close to the base member. Since the fan has no guardmember, it will be seen that this provides a unit which can be readily carried and packed for traveling purposes.

The base and arm-are indicated as made of a phenol condensation product such as' bakelite, but it will be understood that they may be made of other substances such as metal or wood. 4

' In Fig. 8 I have shown a fan in which th I hub is made up of two axially displaced wheels 52 and 53. Theblades in this case are secured to the wheelsby U-shaped metal pieces 54 secured to the wheels. The ribbons are threaded through the members 54 and are riveted or sewed at 55. The vane 12 may be of, leather or material similar to that previously described. It will be seen that my invention is also-applicable to fans of the w rotated What Iclaimiszi.

and a :blade comprising of pliablmmaterial mountedv .at IODgItIIdI- nally remote places of said strip on said memte being of substantially the tween the places. of mounting,

radial flow, type as well as the 'axial flow type. are'of'the'axial'fiow type.

In Fig. 9 I have shown my new fan adapted to the cooling of an automobile radiator 55..' The fan blades 120i non-elastic flexible material are mounted in an extended hub 56.-

56 ly varyin physical forms and that a widevariety 0. materials may be used which may difl'er in some of their characteristics pro-- vided they-are pliable, that is, easily bent or twisted and are of such shape,preferablyf flat or-ribbon-lilre, as to be suitable for blading and having an operatin contour influ-- enced by the action of centri I gal force. It will further be understood that the scope of my invention is not to be limited to the so embodiments illustrated byway of example,

but is to be. determined by the scope of the appendedjclaims when considered in the light o the prior art.

. as L- A fan comprising a retatable member and "a blade comprising 'a strip of pliable material'mounted on said mem er. in slack; condition between spaced places thereon, said stri being bowed outwardly from said member etween saidspacedplaoes due to centrifbeing force on rotation .of said member andmounted so that 'portions thereof provide axially spaced air propelling surfaces, *2. 'A fan comprising. a rotatab e an elongated strip her in slack conditionbetween-spaced places of said member, theside edges of said strip same length be-. part of said strip being constrained by saidmember to have substantially fixed position angularly to the peripheral path of travel of suchpartf F and said strip being tr of mounting to assume centrifu a1 catenary ee between ithe places form and providing air propel ing surface on rotation of said member.

" and a blade comprising 'an elongated st.

3. A fan comprising a; rotatableinching of pliable material mounted at longitudin X remote placesof said strip on said me lnberfin v slack condition between spaced places of said member,- the side edges of .said'strip being ea'ch several times as long-as the direct dis- The arrangements herein described I tially member tanoe between the places of mountin part of'said strip being constrained by sai memberto have substantially fixed position angurlarly to tlf'e' peripheral path of travel of such part, and said strip being free between the places of mounting, to assume centrlfugalcatenary form and'providing air propelling surfaceon rotation of said member.

4. A fan comprising a rotatable member. and a blade comprising an elongatedstrip of pliable material mounted at longitudinally remote places of said strip onsaid member in slack condition between'spaced places of said member, the side edges of said. strip being each substantially longer than the.

direct distance between the places of mou'nting, part of said strip being constrained by said member to have substantially'fixed posi-- tion angularly to the peripheral path of travel of such part, and said strip being free between the places of mounting to assume rotation of said member, a plurality of air propelling surfaces joined remote from the axis of rotation at a substantially tangential portion'ofthe blade 3 5'. A fan comprlsmg a rotatable member and a blade comprising a relatively narrow strip of limp or non-elastic and flexible mate-- rial secured to said member inslack condition between spaced places thereon and part of said strip being constrained by said member to have substantially fixed position angularly to-theperipheral'path of travel of such part.

v6. A fan comprising a rotatable member and a bladecomprising a stri material mounted-on said mem r in slack condition between spaced places thereof, said strip being thrown outwardly like a jump rope from. said member on rotation of said member and part of said strip being) con-' strained by said member to have .su stan-' fixed position angularly to the'p'eriph eral path of travel of such part.

7." A fan" comprising a rotatable member. and a loop blade of ribbon-like pliable material, the end portions of the loop being secured to said member at spaced places thereon with the matgrial in slack condition and at least one offlsaid end portions joining the "tation of saidm'ember.

' 8. A fan comprising and a loop blade comprising a strip of fabric,

of pliable centrifugal catenary form and -providing,,on

;rotatable member obliquely to the axis of ro a a. rotatable member the end portions of saidstrip being secured thestrip in slack condition and lone of said end portions being oblique with respect to the axisv of rotation of said member.

'9. 'A an comprising a'rotatable member to'said member at spacedplaces thereon with e and a blade comprising a ribbon-likestrip of pliable material securedv to said member at axially'spaced' places thereon-and obliquely tothe axis of rotation of said" member, said strip being extensible outwardly from said member between said spaced places.

10. A fan comprising a hub, means for rotatingsaid hub, and a blade comprising an elongated strip of pliable material having places thereof relatively far apart in stretched "condition secured in slack condition between substantially closer spaced places of said hub, the strip being obliquely disposed with respect to the axis of the hub adjacent to one of the places of attachment thereto, said blade being free to assume substantially the form of a centrifugal catenary curve on rotation of the hub.

11. A fancomprising a hub, means for rotating said hub, and a blade, said blade comprising an elongated strip of relatively 12. A fan comprisin a hub, means-for rotating said hub, and ablade, said blade comprising an elongated strip of relatively soft mg a perlpheral surface formed with a pair flexible material having places thereof rela tively far apart in stretched condition secured to said hub in slack condition between substantially closer axially spaced places of said hub and free to be thrown outwardly and to derive its operating contour due to centrifugal force upon rotation of said hub.

and constrained by said hub to provide a lurality of axially spaced air-screw surfaces, said strip being limp when at rest.

13. A fan comprising a hub, means for rotating said hub, and a blade, said blade comprising an elongated strip of relatively soft flexible material secured to said hub at axially and peripherally spacedplaces and adapted to derive its operating contour due to centrifugal force upon rotation of said hub and providin air-screw surface, said strip bein limp w en at rest. I

'14. A fan comprising a hub, means for rotating said hub, and a blade, said blade rality comprising a strip of relatively soft flexible material having places thereof relatively far apart in stretched condition secured at a pluof more closely spaced places on said hub and adapted to derive an operating contour due to centrifugal force of substantially centrifugal catenary form upon rotation of said hub, said strip being angularly disposed with respect to the axis of the hub and its peripheral path of travel at one of the places of attachment thereto and being limp when 7. at rest.

comprising a strip of relatively-soft flexible material having places thereof relatively far apart in stretched condition secured at a plurality of more closely spacedaxially disposed places on said hub and adapted to derive an operating contour due to centrifugal force of substantially centrifugal catenary form upon rotation of said hub, said strip being joined to the hub oblique to the ads of the hub and oblique to its peripheral path of travel and being limp when at rest.

16.' A fan comprising a rotatable member and a loop blade for displacement of air axially of said member upon rotation thereof, said blade comprising a ribbon-like strip of fabric and the ends of the-blade being secured at axially spaced places on said member and arranged obliquely with respect to the axis of rotation of said member.

17, A fan comprising a rotatable member and a loop blade for displacement of air axially of said member upon rotation thereof, said blade comprising a ribbon-like strip of relatively soft pliable material, the ends of said blade being secured to said member at axially spaced places and joining said member along curved lines generally oblique to the axis of rotation of said member.

' 18. A fan-comprising a rotatable hub havof spaced slots at least one of which extends angularly with respect to the axis of rotation of the huband a ribbon-like strip of relatively soft pliable material providinga loop blade having-ends secured in said slots.

19. A fan comprising a rotatable hub, said hub being formed with a .pair of axially spaced slots on the periphery thereof extending) obliquely to the axis of rotation of the hu and; a ribbon-like strip comprising pliable fabric providing a loop blade having ends secured in said slots.

20. A fan comprising ahollow rotatable hub, said hub being formed with a pair of spaced slots extending through the peripheral wall of the hub, at least one of said slots being dis osed at an angle with respect to the axis 0 rotation of the hub, and a ribbon-likestrip of pliable material providing a loop blade having ends as'singlthrough said slots to the interior 0 said ub, said ends being enlarged 'within the hub to prevent them from being withdrawn through said slots due to centrifugal force acting on said strip.

In testimony whereof I'hereunto aflix my signature. ,7

FREDRIK LJ'UNGSTROM. 

